Metal soap grease containing alkaline earth metal alkyl phenol sulfide



United States PatentO METAL SOAP GREASE C(DNTAINING ALKALINE EARTH METALALKYL PHENOL SULFIDE John P. Dilworth, Fishkill, N. Y., Charles H.Culnane, Grosse Ile, Mich, and Harry V. Ashburn, deceased, late ofBeacon, N. Y., by Evelyn L. Ashburn, administratrix, Beacon, N. Y.,assignors to The Texas Company, New York, N. Y., a corporation ofDelaware No Drawing. Original application April 18, 1951, Serial No.221,742. Divided and this application February 19, 1953, Serial No.337,874

4 Claims. (Cl. 25242.1)

This invention relates to a lubricating grease composition, andparticularly to such a composition which is inhibited against coppercorrosion.

This is a division of our co-pending application Serial No. 221,742,filed April 18, 1951, now'Patent Number 2,690,998.

Lithium base lubricating grease compositions have found substantial usein aircraft controls and for other purposes where operation over a widetemperature range, and particularly operation at extremely lowtemperatures, is encountered. U. S. Patent No. 2,450,221, Ashburn,Barnett and Puryear, is typical of a superior lithium base grease ofthis type prepared from a lithium soap of a hydroxy fatty acid or theglyceride thereof, such as hydrogenated castor oil, and containing asthe major proportion of the liquid lubricating base an oil soluble highmolecular weight high boiling liquid aliphatic dicarboxylic acid esterwithin the lubricating oil viscosity range and possessing lubricatingproperties. As disclosed therein, the lithium soap may be formed from amajor proportion of the hydroxy fatty acid or glyceride thereof, and aminor proportion of a saturated fatty acid, the grease containing asmall excess of free fatty acid. Such greases have exceptional shear andtexture stability over a wide temperature range and excellent lowtemperature properties.

Whilethe lithium base greases of the aforesaid type have provedeminently satisfactory in service, the increased use of copper andcopper alloys in certain applications particularly in aircraft andartillery control instruments, has introduced an additional problem ofrendering the grease non-corrosive to copper in long time service. Forthis purpose, U. S. Army Specification 2134 has prescribed a rigorouscopper corrosion test for qualification under this specification. Inattempting to meet this specification, it has been found that corrosioninhibitors heretofore employed in greases are ineffective. f

One of the principal objects of the present invention is to provide alubricating grease which satisfactorily meets the copper corrosion testof U. S. Army Specification 2-134.

Another object of the present invention is to provide a lithium basegrease which retains all the desirable properties of the previouslyknown greases of this type, including shear and texture stability over awide temperature range and excellent low temperature properties, and atthe same time is eifectively inhibited against corrosion of copper andcopper alloys in long time service.

In accordance with the present invention, the foregoing objects havebeen attained by incorporating in the grease about 0.25 to 5% by weightof an oil-soluble alkaline earth metal salt of an alkyl phenol sulfidehaving a total of to 30 carbon atoms in the alkyl substituents on eachbenzene nucleus. Salts of this type have heretoforebeen suggested asdetergent additives for mineral lubricating oils; but it was entirelyunexpected that such salts would function in the present greases ascopper corrosion inhibitors, since this action is completely remote fromdetergency.

The alkaline earth metal salts which are effective copper corrosioninhibitors for purposes of the present invention, are prepared fromthealkyl phenol sulfides having the structural formula where R is analkyl group containing 5 to 30 carbon atoms, )1 represents the number'of alkyl substituents on each benzene nucleus and is generally 1 or 2,with the proviso that the total number of carbon atoms of the alkylsubstituents on each benzene nucleus is at least 10, and x is either 1or 2. The alkaline earth metal salts may be either normal salts whereinthe alkaline earth metal completely neutralizes the OH groups of 2molecules of the alkyl phenol, producing the compound having the formula-Sz- Rn Rn where M represents the alkaline earth metal, or may be thebasic salt having the formula OMOH OMOH These various compounds may beprepared in known manner by the alkylation of a phenol sulfide with aselected olefin or olefin polymer of the proper chain length, namelyfrom 5 to 30 carbon atoms, in the presence of a suitable alkylationcatalyst, such as HF, BFs, and the like. The .olefin polymer ispreferably prepared by polymerizing propylene under pressure, using forexample a BFs-HzO catalyst. Likewise butylene polymer can be used.Depending upon the conditions of the alkylation, the phenol sulfide maybe monoor dialkylated. Where a lower molecular weight olefin, such asamylene is employed for alkylation, the phenol sulfide is dialkylated toprovide a total of at least 10 carbon atoms in the substituent alkylgroups. Where a high molecular weight olefin is employed, such forexample as a propylene polymer fraction having olefins of 15 to 30carbon atoms in the molecule, the product is generally monoalkylated. Inaddition to simple phenol sulfide, other sulfides of monohydroxymononuclear aromatic compounds'having the hydroxyl group attached to thering can be employed as the starting material, such for example as thecresols, xylenols and other alkyl phenols. In the following descriptionand claims, all of these various alkylated compounds will be referred toas alkyl phenol sulfides.

The foregoing alkyl phenol sulfides in solution in a suitable aromaticsolvent, such as toluene, are then reacted with the alkaline earth metalcompound to produce the corresponding alkaline earth metal salt. Any ofthe alkaline earth metals, including calcium, barium, strontium andmagnesium can be employed, although barium and magnesium are generallypreferred. In the manufacture of a magnesium alkyl phenolate sulfide,for example, the alkyl phenol sulfide in toluene solution maybereactedwithmagnesium methylate dissolved in excess methyl alcohol at atemperature-of about 40-50 C., using slightly less than one mol of themagnesium methylate per mol of the alkyl'phenol sulfide. The temperatureis then'increased and the-methyl alcohol distilled off. The resultingtoluene solutionof magnesium alkyl phenolate sulfide, which is thenormal salt represented-byformula No. 2 above, is-filtered while hot;and then sufficient mineral lubricating oil, such as a distillate oilhaving an SUS viscosity at 100 F. of about 300, is added to produce anultimate -to 50% concentrate of the magnesium alkyl phenolate sulfide inthe lubricating oil. The toluene solvent is then stripped from thelubricating oil concentrate.

In preparing a basic alkaline earth metal salt of the foregoing alkylphenol sulfides, the latter are preferably reacted with a substantialexcess of an aqueous solution of a watersoluble alkaline earth metalsalt. For example, inzpreparinga basic barium alkylphenolate sulfide, anaqueous-solution of barium chloride with the latter in excess ofthat'required'for neutralization is added to a lubricatingoil solutionof the alkyl phenol sulfide. The reaction mix is subjected to steamingwith agitation for a substantial period of time, such as about 1-4hours. Following separation of the aqueous.phase,'the lubricating oilsolution of the basic barium alkyl phenolate sulfide is washed and thenheated to remove residual mixture to obtain a lubricating oilconcentrate of the desired additive in about 25-50% concentration. Thebasic salts may also be prepared by reacting an oil solution of thealkyl phenol sulfide witha methanolsolution of an excess of bariumhydroxide, and then removing the methanol.

. Typical compounds prepared as outlined above and which are useful forpurposes of the present invention are barium diamyl phenolatemonosulfide, barium diamyl phenolate disulfide, basic barium cardanolatesulfide formed from hydrogenated cardanol, magnesium alkyl phenolatemonosulfide or disulfide wherein the alkyl group contains from 15 tocarbon atoms and is preferably C18 to Czs, and similar compounds of theother alkaline earth metals. Instead of preparing the alkylphenolsulfide by alkylation as described above, suitable .alkyl phenolsulfides containing at least 10 carbon atoms in the alkyl substituentsoneach benzene nucleus can be used, such as the hydrogenated cardanolatesulfide as specified above.

The above described alkaline earth metal salts of alkyl phenol sulfidesmay be employedin lithium base greases formed from any saturated fattymaterial, such as the conventional saturated fatty acids or glyceridesthereof, to provide copper corrosion inhibition.

Preferably, the lithium base greases formed from hydroxy fatty acids ortheir corresponding glycerides, such as hydrogenated castor oil, areemployed to obtain the improved shear and texture stability. Suitabletypes of soap-forming hydroxy fatty acids and glycerides thereof aredisclosed in said Patent No. 2,450,221. While the soapforming hydroxyfatty acids or their glycerides may be used as the sole acidic componentof the lithium soap, they may be blended or combined with theconventional saturated fatty acids or fats in such proportions that atleast 50% of the total acidic component iscomprised of the hydroxy fattyacids or glyceridesthereof. In general, any of the recognized fatty acidmaterials normally used in grease manufacture may be employed providingthey are essentially saturated in character. These fats'and fatty acidsinclude mixtures of fatty acid glycerides found in naturally occurringfats and oils, together with fractionated components thereof. The fattyacids may be a mixture of acids split oif from these fats or prepared byhydrogenation of fish oils, or the individual acids themselves.Verysatisfactory results are secured by employing as the. saturatedfatty material for the formation of the lithium soap a mixture'of about60-80% of. hydrogenated castor nil or 12-hydroxy :stearic :acid,with-40- 20% of a saturated fatty acid such as stearic acid. The

1 grease may contain about lO-30% by weight of the lithium soap.

In order to obtain the improved wide temperature range and lowtemperature properties, the liquid lubricating base of the lithiumgrease composition is preferably formed of a major proportion of asynthetic oleaginous lubricating compound or condensation product, manytypes of which are now known in the art. Very satisfactory syntheticlubricants of this character are represented by the high molecularweight high boiling liquid aliphatic dicarboxylic acid esters which arewithin the lubricating oil viscosity range and possess lubricatingproperties. The compounds within this particular class are the esters ofsuch acids as sebacic, adipic, pimelic, azelaic, alkenyl succinic,alkylmaleic, etc. The esters thereof are preferably the aliphatic estersand particularly the branched chain aliphatic diesters. Specificexamples of the preferred oleaginous compounds are di- 2ethylhexyl-sebacate, di-Z-ethyl hexyl azelate, di-2-ethyl hexyl adipate,di-sec-amyl sebacate, di-2-ethyl hexyl alkenyl succinate,di-2-ethoxyethyl sebacate, di-2-(2'- methoxyethoxy) ethyl sebacate,di-2-(2'-ethyl butoxy) ethyl sebacate, di-2-butoxy ethyl azelate, di-2(2-butoxy ethoxy) ethyl alkenyl succinate, etc.

These oleaginous compounds may be used as the sole oil component of thegrease or they may be blended with a mineral lubricating oil. Where ablend is em- I ployed, and low temperature properties are required, the

mineral lubricating oil is preferably a light refined distillate minerallubricating oil, such as a naphthene or parafiin base distillate, havingan SUS viscosity at F. of about 50130 and preferably about 100 secs. The

' mineral lubricating oil will generally constitute less than 50% of-theblend, and ordinarily about 40-20% thereof. The mineral lubricating oilblend is advantageous where the lithium soap is formed in situ. In suchcase, the saponification of the fatty material with the lithiumhydroxide and dehydration of the resulting soap are'conveniently carriedout in the presence of a portion of the mineral lubricating oil, and thesynthetic lubricant together with the additives employed in the greaseare then added following dehydration and as the agitated soap mix cools.

The following examples are given toillustrate the present invention:

EXAMPLE 1 A lithium base grease was prepared from a fatty materialconsisting of about 75 by weight of hydrogenated castor oil and 25% byweight of stearic acid. The lubricating base used was a mixture of about75% by weight of di-Z-ethyl hexyl azelate with about 25% by weight of aparaffin base mineral lubricating oil having an SUS viscosity at 100 F.of about 100. The method of preparation-involved charging a steam heatedkettle with the required amount of 10.3% lithium hydroxide solutiontogether with a small amount of water, the hydrogenated castor oil and asmall proportion of the parafiin base mineral lubricating oil, thelatter being less than the amount of hydrogenated castor oil andgenerally about /2. to of the latter. The kettle contents were held at-190 F. for about 4 hours with agitation, and then the stearic acid wasadded and the temperature maintained with stirringfor'another 1-2 hoursto complete saponification. Following saponification, a 25% concentrateof an octyl methacrylate ester polymer in a mineral lubricating oil,which is sold commercially by Rohm and Haas under the name AcryloidHF-600, was added in an amount to provide 2% by weight of theconcentrate in the final grease composition. The feature of addingmethacrylate ester polymers of this type to a lithium base ball androller bearing grease for the purpose of noise suppression in bearingsoperated at high speeds is disclosed and claimed in the co-pendingapplication of Dilworth, Finn and Puryear, Serial No. 220,538, filedApril I1,

1951." The saponified mix was then heated with stirring at 290 to 330 F.for about 4 hours to effect dehydration. The balance of the minerallubricating oil was then added with stirring as the kettle contentscooled 6 for no pressure drop during the test, and this item is notseparately listed in the table.

Samples 1-3 inclusive of the foregoing table represent the base greaseof Example 1, and the base grease comdown to about 280 F. The di-2-ethylhexyl azelate was 5 pounded with 1% and 3% respectively of Paranox 56.then slowly added with stirring as the mix continued to As will be notedfrom the calculated composition of the cool to about 220 F. Phenylalphanaphthylamine in an base grease, a calculated excess of 0.2% byweight of amount of about 0.5% by weight based on the grease was lithiumhydroxide was employed in preparing this grease; then added as anoxidation inhibitor, and a small amount and, as shown by the table thegreases of samples 1-3 of a dye was introduced. The resulting basegrease was analyzed to a free alkali content, calculated as lithiumdrawn at a temperature below 200 F. hydroxide, of 0.09%. It is to benoted that the base The resulting base grease had the followingcalculated grease of sample 1 produced a grey stain on the coppercomposition: strip and a pink discoloration on the grease, and thusfailed the test. Samples 2 and 3 containing the Paranox Lithium Soap ofhydrogenated Castor oil Welght fg 56 successfully passed this rigorouscopper corrosion Lithium Stearate test. In this 0011212111011, a??? a};giscloged 11113116 2233132- u ing app ication o eorge c ert, eria o. lgt z iin ee om saponification of hydrogenated 0.2 l February 5 PatentCastor on) 1.3 nized copper corrosion inhibitors Wl'llCh are eifective1n Paraffin base lubricating oil 19.7 20 other relationships arecompletely ineffective for purposes Di z ethyl hexyl azelate 59 2 of thepresent invention. It was entirely unexpected that Phenylalphanaphthylam'irlg a material, such as an alkaline earth metal salt ofan Acryloid alkylphenol sulfide, wh ch is recognized as a detergent Dyed addit ve for lubricating 0115, such as motor OllS, should be effectiveas a copper corrosion inhibitor in the new en- To different portions ofthe foregoing base grease, varvironment of a lithium base grease. iousamounts of barium diamyl phenolate sulfide, which In the aforementionedEckert application, the use of a is solid commercially by the EnjayCompany, Inc. as different type of copper corrosion inhibitor,namelyabasic Paranox 56, were added as shown in samples 2 and 3 alkalineearth metal sulfonate, in a lithium base grease in the following table.The said greases were then subof this character is disclosed andclaimed; and, further, jected to the copper corrosion test of the 2134specifiit is pointed out that the grease should be prepared to cationwith the results as shown in the table. a calculated excess alkalinityin order for this different Table 2-134 Cu Corrosion Test Additive, wt.Rating Copper Grease 1. Base Grease- Grey stain Pintk discolor- Fail. 2.Base Grease-.. +1%Paranox56 Very slight N3 ch ngeun Pass. 3. BaseGrease.-- +3%Paranox 56- ol e r l i do D0. 4. Base Grease--.+1%Paranox56 Borderline to 5. Base Grease--. +0.7%Paranox56 Sta P l 6.Base Grease-.. +0. 1%Paranox56- 7. Base Grease... +3.0%Paranox 56- (1),(2) and (3) Free alkali (LiOH). (4) Free fatty acid (oleic) (5) Freealkali (LiOH) (6) Free alkali (LiOH) (7) Prepared with di-2-ethyl hexylsebacateiree fatty acid (oleic) The 2-134 corrosion test of theforegoing table was run by placing a copper strip in a Norma-Hofimanbomb so as to be partially immersed in the sample of the grease undertest, and then maintaining the bomb under oxygen pressure (110 poundsper sq. in. initial pressure) at 210 F. for 20 hours. During thatperiod, no pressure drop due to oxygen absorption must occur. Then, atthe completion of the 20-hour period, both the sample of grease andcopper strip are inspected. In addition to the requirement for nopressure drop during the test, there must be no more than a very faintstain on the copper strip and no more than a slight stain on the greasein order to be rated as passing. Slightly inferior products which do notmerit a full pass rating are given a rating of borderline to pass wherethere is no more than a light strain on the grease and no pressure drop;and a rating of borderline to fail where there is a stain on the copperwith or without a stain on the grease and no type of copper corrosioninhibitor to be uniformly effective in the said 2-134 test. Samples 47of the foregoing table show that this requirement of excess alkalinityis obviated by the copper corrosion inhibitors of the present invention.Thus sample 4 represents a grease prepared in accordance with Example 1above except that a slight excess of stearic acid was used so that thegrease analyzed to a free fatty acid content, calculated as oleic, of0.23% by weight. As shown, 1% of Paranox 56 in this grease gave aborderline to pass rating in the 2-134 copper corrosion test. Sample 7of the table represents a grease prepared in accordance with Example 1above, except that di-Z-ethyl hexyl sebacate was employed as the majorportion of the lubricant base instead of the corresponding azelate, andalso an excess of stearic acid was again used in the formulation. 3% ofParanox 56" in this particular grease gave a clear pass rating. Samples5 and 6 of the table were prepared in accordance with Example 1 above,using a calculated excess of lithium hydroxide of 0.3% and 0.2%respectively. It will be noted that as little as 0.4% by weight ofParanox 56 in this grease gas a pass rating.

While the additives of the present invention have been specificallydescribed above in connection with lithium base greases because theseare representative of the type generally employed for specialty widetemperature range, and particularly low temperature service, it is to beunderstood that the invention is not limited thereto. Rather, theinvention is also applicable to the improvement of the copper corrosionproperties of other metal base greases, including those of sodium,calcium, aluminum, barium, and mixed base greases. For example, a greasecomprising an oleaginous liquid lubricating base, such as a minerallubricating oil or a synthetic lubricant base or mixture thereof,thickened to a grease-like consistency with about 10-30% of calcium12-hydroxy stearate, may have added thereto for copper corrosioninhibition about 0.25-% by weight of an alkaline earth metal salt of aphenol sulfide of the type described above. The invention isparticularly applicable to various metal base greases wherein thesoap-forming fatty material of the metal soap consists of at least 50%by weight of hydroxy fatty acids or the glycerides thereof, such as12-hydroxy stearic acid and hydrogenated castor oil.

It will be understood that the grease of the present invention may alsocontain other additives in small proportions which are compatible withthe essential ingredients and do not interfere with the desirableproperties thereof. Such additional additives include extreme pressureor lubricity agents, such as dibenzyl disulfide and tricresyl phosphate,materials for improving resistance in the salt spray humidity cabinettest, such as sorbitan mono-oleate, and the like.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

We claim:

1. A lubricating grease composition comprising as the essentialconstituents an oleaginous liquid lubricating base of. which at leastthe major proportion is a high boiling liquid aliphatic dicarboxylicacid ester, about -30% by weight of a lithium soap of a saturatedsoap-forming fatty material, said grease normally being corrosive tocopper, and from 0.25 to 5% by weight based on said composition ofbarium diamyl phenolate sulfide in sutficient proportion to enable saidgrease composition to pass the copper corrosion test of U. S. Armyspecification 2-134.

2. A lubricating grease composition comprising as the essential and amajor proportion of the lubricating base an oil-soluble high molecularweight high-boiling liquid aliphatic dicarboxylic acid ester within thelubricating viscosity range and possessing lubricating properties,sufficient lithium soap of soap-forming fatty material to thicken saidlubricant base, said soap-forming fatty material consisting of more than50% by weight of a hydroxy soap-forming fatty material selected from thegroup consisting of hydroxy fatty acids and hydroxy fatty acidglycerides, said grease normally being corrosive to copper, and from 0.5to 3% by weight based on said composition of barium diamyl phenolatesulfide in sufiicient proportion to enable said grease composition topass the copper corrosion test of U. S. Army specification 2-134.

3. A lubricating grease composition comprising as the lubricant base amixture of substantial proportions each of mineral lubricating oil and abranched chain aliphatic diester of a dicarboxylic acid selected fromthe group consisting of sebacic, azelaic and adipic acids, with saiddiester being in major proportion of the said mixture, about 10-30% byweight based on the composition of lithium soap of a mixture of a majorproportion of hydrogenated castor oil and a minor proportion of stearicacid, said grease normally being corrosive to copper, and from 0.5 to 3%by weight based on said composition of barium diamyl phenolate sulfidein sufficient proportion to enable said grease composition to pass thecopper corrosion test of U. S. Army specification 2-134.

4. A lubricating grease composition consisting essentially of thefollowing constituents in the approximate percentages by Weight:

Di-2-ethyl hexyl sebacate 50-85 Lithium soap of a 2:1 to 4:1 weightmixture of hydrogenated castor oil and stearic acid 10-30 Phenyl alphanaphthyl amine 0.3-1.0 Barium diamyl phenolate sulfide 0.5-3.0 Minerallubricating oil Balance References Cited in the file of this patentUNITED STATES PATENTS 2,351,384 Woods et al June 13, 1944 2,362,289Mikeska Nov. 7, 1944 2,362,291 Winning Nov. 7, 1944 2,362,292 McNab Nov.7, 1944 2,397,956 Fraser Apr. 9, 1946 2,409,303 Morris et al Oct. 15,1946 2,450,222 Ashburn Sept. 13, 1948 2,461,335 Mikeska Feb. 8, 19492,480,664 McNab et al Aug. 30, 1949 2,483,505 Rogers Oct. 4, 19492,518,379 Rogers Aug. 8, 1950

1. A LUBRICATING GREASE COMPOSITION COMPRISING AS THE ESSENTIALCONSTITUENTS AN OLEAGINOUS LIQUID LUBRICATING BASE OF WHICH AT LEAST THEMAJOR PROPORTION IS A HIGH BOILING LIQUID ALIPHATIC DICARBOXYLIC ACIDESTER, ABOUT 10-30% BY WEIGHT OF A LITHIUM SOAP OF A SATURATEDSOAP-FORMING FATTY MATERIAL, SAID GREASE NORMALLY BEING CORROSIVE TOCOPPER, AND FROM 0.25 TO 5% BY WEIGHT BASED ON SAID COMPOSITION OFBARIUM DIAMYL PHENOLATE SULFIDE IN SUFFICIENT PROPORTION TO ENABLE SAIDGREASE COMPOSITION TO PASS THE COPPER CORROSION TEST OF U. S. ARMYSPECIFICATION 2-134.